Technical Field of the Disclosure
The present embodiment relates in general to fluid extrusion application systems and methods. More specifically, the present disclosure relates to a system and method providing for the precise application of glue by controlling glue pressure in relation to a desired volume of the glue to be deposited on a moving substrate.
Description of the Related Art
Labeling systems are used in a wide variety of manufacturing operations to apply labels on a product so that one product may be differentiated from another. Glue extruding machines are used in the labeling system for applying glue while labeling the bottles, containers, cans, boxes and other products available in the market. Different methods and systems have conventionally been used to label such products. A common method is the roll of label that is presented in the form of a web and is glued at the edges and wrapped around the circumference of the products. Another method includes a web carrier having labels which are attached to the product with pressure sensitive adhesives. Various other forms of systems and methods of application are widely known and practiced.
The conventional systems have issues related to precise control of glue quantity, consistency of glue properties and volume of glue required to secure a label while applying glue to labels at a high rate of speed. In some systems, the glue will splatter to the vacuum drum while applying glue to the label. Thus, removal of the splattered glue may require periodic cleaning with solvents and may result in machine downtime. Sometimes, reheating of the glue may adversely affect properties of the glue and exposure of the glue to air may result in degradation of the adhesive properties of the glue.
One approach for compensating the above problems includes a label delivery system that suggests spraying a container with hot melt glue to adhere a leading end of a label from a cut and stack label magazine or a roll fed labeler to the container. The glue is applied onto the trailing edge of the label by a slit die nozzle that directly contacts the label to apply glue to the trailing edge that is then attached to the container or the label. However, the glue extruded from the nozzle remains for some time on the head until the glue is smeared onto the trailing edge of the label. In addition, when the labeling speed increases the quantity of the glue laid down on the label varies and fails to provide a method of controlling the lay down weight at variable speeds. Thus, due to the variation in lay down weight the label may become jammed in the machine or otherwise misapplied to the container. In certain systems, when the slit die nozzle directly contacts the label for glue application, particularly with thinner labels, the label may be wrinkled or otherwise distorted.
In other approaches, glue is provided to the slit die nozzle at a pressure that is controlled with the objective of maintaining a constant pressure level. However, the glue is distributed in an uneven manner when the valve is opened and closed to apply the glue to the label. Another strategy for applying glue is to control the volume of glue applied by changing the speed of the glue pump in an effort to maintain a constant pressure. One problem with this approach is that it may result in an intermittent pattern of pressure spikes and thickness variation in the adhesive deposits. Thus, the label cannot be applied to the bottles or containers properly.
Another approach describes a device and a method for spray extrusion having a source of coating material connected to a nozzle for spraying the material onto an object. The nozzle has a discharge aperture in the form of a pattern of holes, preferably a row of holes. However, the distance between the nozzle and the object is often too large and when that occurs the jet will not reach the object adequately. In addition, a region of increased pressure is created in the nozzle, causing the material to be sprayed out of the nozzle onto the object at a relatively high discharge velocity and thus the quantity of glue applied is subject to variation.
Yet another approach describes a labeling machine that applies an adhesive to labels for attachment to containers and has a glue bar which engages a glue roller. A label drum receives and delivers labels into engagement with containers for wraparound labeling of the containers. An adhesive is delivered to the glue bar. The adhesive is a hot melt adhesive which can maintain its label bond while withstanding high heat such as from a pasteurization process. The hot melt adhesive has a viscosity which tends to increase if the adhesive is not kept in constant motion or is allowed to set. The shear of the adhesive is increased during adhesive transfer to ensure low viscosity transfer of the adhesive from the glue roller to a label positioned on the label drum. The low viscosity transfer of the adhesive does not yield a consistent and reliable application of glue exhibiting a controlled thickness when the speed of application changes. The hot melt adhesive is a compressible non-Newtonian liquid which renders volumetric control unreliable because it does not compensate for internal friction, the Reynolds number for the passages, changing viscosity and changes in shear strength caused by the speed of flow of the glue.
Attempts have been made to compensate for this instability by variably controlling the pressure upon the speed of extrusion and the flow characteristics of the glue. Such systems describe a machine and a method of applying a non-Newtonian liquid composition onto a surface in a controlled manner to obtain desired target deposit thickness and consistent lay down weights. The composition is held in a chamber at a controlled variable pressure and is dispensed through a slit die nozzle as controlled by a valve. Characteristics of the composition are empirically developed and provided to a logic control circuit to assure that the composition is dispensed on either the entire surface or in one or more precise locations. However, there exists a gap between the vacuum drum and the nozzle during this process. Also, such systems require an additional return conduit having an orifice to retrieve a small portion of the glue to a glue reservoir through the return conduit to control the pressure of the glue.
Therefore, there is a need for a system and method providing precise application of glue by controlling glue pressure in relation to a desired volume of the glue to be deposited on a moving substrate. Such a system would include a gun and a nozzle to apply glue to a leading edge and a trailing edge of the moving substrate respectively without any variation in the thickness or glue pattern. Such a system and method would include a gear pump that would regulate the extrusion of the glue onto the moving substrate that is programmed with data representative of a gear reducer ratio at which the glue flows within a constant speed, torque, current, speed and a position of the glue at a desired temperature. Such a system and method would eliminate a gap between an applicator drum and a nozzle as a trailing edge of the moving substrate is blown off over to the nozzle to receive a smear of glue in a controlled manner. Such a needed system and method would allow the gear pump to adjust glue pressure to achieve a precise pressure related to volume of a glue deposition and speed of the moving substrate onto which glue is applied by calculating a difference between a changed gear reducer ratio and a predetermined gear reducer ratio. Finally, this needed system would be simple in construction, would not require any additional return conduit to retrieve glue to a glue reservoir to control the pressure of the glue and apply labels to the bottles or containers properly. The present invention overcomes the prior art shortcomings by accomplishing these objectives.